Quantum interference device, atomic oscillator, and moving object

ABSTRACT

An atomic oscillator includes: a gas cell which includes two window portions having a light transmissive property and in which metal atoms are sealed; a light emitting portion that emits excitation light to excite the metal atoms in the gas cell; a light detecting portion that detects the excitation light transmitted through the gas cell; a heater that generates heat; and a connection member that thermally connects the heater and each window portion of the gas cell to each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. application Ser. No.14/177,497 filed Feb. 11, 2014 which claims priority to Japanese PatentApplication No. 2013-029167, filed Feb. 18, 2013 both of which areexpressly incorporated by reference herein in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to a quantum interference device, anatomic oscillator, and a moving object.

2. Related Art

An atomic oscillator that oscillates based on the energy transition ofatoms of alkali metal, such as rubidium and cesium, is known. Ingeneral, the operating principle of the atomic oscillator is largelydivided into a method using a double resonance phenomenon caused bylight and a microwave and a method using coherent population trapping(CPT) caused by two types of light components having differentwavelengths.

In the atomic oscillator of any method, in order to seal alkali metal ina gas cell together with buffer gas and keep the alkali metal in a gasstate, it is necessary to heat the gas cell to a predeterminedtemperature. In addition, excitation light for exciting the alkali metalis emitted into the gas cell, and the intensity of the excitation lighttransmitted through the gas cell is detected.

In general, in the gas cell, all of the alkali metal is not gasified,but a part of the alkali metal is present as liquid as a surplus. Thesurplus alkali metal is liquefied by being deposited (condensed) on alow-temperature portion of the gas cell.

When such surplus alkali metal atoms are present in the excitation lightpassage area, the alkali metal atoms block the excitation light. As aresult, the oscillation characteristics of the atomic oscillator aredegraded.

Therefore, for example, in an atomic oscillator disclosed inJP-A-2009-302706, a plurality of heaters are disposed on each of theexcitation light incidence surface and the excitation light emissionsurface of the gas cell in which gaseous metal atoms are sealed.

In the atomic oscillator disclosed in JP-A-2009-302706, however, sincethe heaters are disposed next to the gas cell, there has been a problemin that an unnecessary magnetic field generated in the heaters bycurrent application acts on the alkali metal in the gas cell and thisdegrades the oscillation characteristics. In particular, when aplurality of heaters are provided, if the amount of current applicationto each heater is changed to keep the temperature in the gas cellconstant, the above-problem becomes noticeable since not only themagnitude but also the direction of the unnecessary magnetic field ischanged.

In addition, in the atomic oscillator disclosed in JP-A-2009-302706,since a plurality of heaters are provided, for example, the number ofwiring lines to the heaters is increased. As a result, there has alsobeen a problem in that the entire atomic oscillator becomes large.

SUMMARY

An advantage of some aspects of the invention is to provide a quantuminterference device and an atomic oscillator that can be miniaturizedand can suppress the influence of an unnecessary magnetic field from aheating portion, which generates heat by current application, on a gascell and to provide a moving object with excellent reliability thatincludes the atomic oscillator.

The invention can be implemented as the following forms or applicationexamples.

Application Example 1

This application example is directed to a quantum interference deviceincluding: a gas cell including two window portions having a lighttransmissive property and a side wall that seals metal atoms togetherwith the two window portions; a light emitting portion that emits lightthat is transmitted through one of the window portions to excite themetal atoms; a light detecting portion that detects the light passingthrough the metal atoms and transmitted through the other windowportion; a heating portion that generates heat; and a connection memberthat includes a material having a larger thermal conductivity than amaterial forming the side wall and that thermally connects the heatingportion and each of the two window portions to each other.

According to the quantum interference device, since the heating portionis thermally connected to each of the two window portions of the gascell through the connection member, heat from the heating portion can betransmitted to each window portion by thermal conduction using theconnection member. As a result, each window portion can be heated. Inaddition, the heating portion and the gas cell can be separated fromeach other. Accordingly, it is possible to suppress a situation wherethe unnecessary magnetic field caused by the application of current tothe heating portion has an adverse effect on the metal atoms in the gascell. In addition, since the number of heating portions can be reduced,the number of wiring lines for the application of current to the heatingportion can be reduced. As a result, it is possible to miniaturize thequantum interference device.

Application Example 2

This application example is directed to a quantum interference deviceincluding: a gas cell including two window portions having a lighttransmissive property and a side wall that seals metal atoms togetherwith the two window portions; a light emitting portion that emits lightthat is transmitted through one of the window portions to excite themetal atoms; a light detecting portion that detects the light passingthrough the metal atoms and transmitted through the other windowportion; a heating portion that generates heat; and a connection memberthat contains a material having a larger thermal conductivity than amaterial forming the side wall and is connected to the two windowportions, a part of the connection member facing the heating portion.

According to the quantum interference device, since the heating portionfaces a part of the connection member, heat from the heating portion canbe transmitted to the connection member. In addition, since theconnection member is connected to each of the two window portions of thegas cell, heat from the heating portion can be transmitted to eachwindow portion by thermal conduction using the connection member. As aresult, each window portion can be heated. In addition, the heatingportion and the gas cell can be separated from each other. Accordingly,it is possible to suppress a situation where the unnecessary magneticfield caused by the application of current to the heating portion has anadverse effect on the metal atoms in the gas cell. In addition, sincethe number of heating portions can be reduced, the number of wiringlines for the application of current to the heating portion can bereduced. As a result, it is possible to miniaturize the quantuminterference device.

Application Example 3

In the quantum interference device according to the application example,it is preferable that a heat transfer layer, which contains a materialhaving a larger thermal conductivity than a material that forms each ofthe window portions, is disposed on a surface of each of the windowportions.

With this configuration, heat from the connection member can beefficiently diffused by thermal conduction using the heat transferlayer. As a result, it is possible to make the temperature distributionof each window portion uniform.

Application Example 4

In the quantum interference device according to the application example,it is preferable that each of the window portions and the connectionmember is connected to each other through the heat transfer layer.

With this configuration, heat from the connection member can beefficiently transferred to each window portion.

Application Example 5

In the quantum interference device according to the application example,it is preferable that the connection member has a pair of connectionportions, which are provided with the gas cell interposed therebetweenin a direction in which the two window portions are aligned, and aconnecting portion that connects the pair of connection portions to eachother.

With this configuration, heat from the heating portion can beefficiently transferred to each window portion.

Application Example 6

In the quantum interference device according to the application example,it is preferable that the connecting portion has a portion separatedfrom the gas cell.

With this configuration, since the transfer of heat between theconnecting portion and the gas cell can be suppressed, heat can beefficiently transferred from the connection member to each windowportion.

Application Example 7

In the quantum interference device according to the application example,it is preferable that the connection member contains a soft magneticmaterial, and at least a part of the connection member is disposedbetween the gas cell and the heating portion.

With this configuration, it is possible to prevent a magnetic field fromthe heating portion from reaching the gas cell.

Application Example 8

In the quantum interference device according to the application example,it is preferable that the heating portion is separated from the gascell.

With this configuration, it is possible to suppress a situation wherethe unnecessary magnetic field caused by the application of current tothe heating portion has an adverse effect on the metal atoms in the gascell.

Application Example 9

This application example is directed to an atomic oscillator includingthe quantum interference device described above.

With this configuration, it is possible to provide an atomic oscillatorthat can be miniaturized and can suppress the influence of anunnecessary magnetic field from the heating portion, which generatesheat by current application, on the gas cell.

Application Example 10

This application example is directed to a moving object including thequantum interference device described above.

With this configuration, it is possible to provide a moving objecthaving excellent reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a cross-sectional view showing an atomic oscillator (quantuminterference device) according to a first embodiment of the invention.

FIG. 2 is a schematic diagram of the atomic oscillator shown in FIG. 1.

FIG. 3 is a diagram for explaining the energy state of alkali metal in agas cell of the atomic oscillator shown in FIG. 1.

FIG. 4 is a graph showing the relationship between the frequencydifference of two light components from a light emitting portion and thedetection intensity in a light detecting portion for the light emittingportion and the light detecting portion of the atomic oscillator shownin FIG. 1.

FIG. 5 is a cross-sectional view for explaining a heating portion and aconnection member of the atomic oscillator shown in FIG. 1.

FIG. 6 is an exploded view for explaining the gas cell and theconnection member of the atomic oscillator shown in FIG. 1.

FIG. 7 is a plan view for explaining the gas cell and the connectionmember of the atomic oscillator shown in FIG. 1.

FIG. 8A is a plan view for explaining a support member of the atomicoscillator shown in FIG. 1, and FIG. 8B is a cross-sectional view takenalong the line A-A in FIG. 8A.

FIG. 9 is a cross-sectional view showing an atomic oscillator (quantuminterference device) according to a second embodiment of the invention.

FIG. 10 is a plan view for explaining a gas cell and a connection memberof the atomic oscillator shown in FIG. 9.

FIG. 11 is a diagram showing the schematic configuration when the atomicoscillator according to the embodiment of the invention is used in apositioning system using a GPS Satellite.

FIG. 12 is a schematic block diagram showing an example of a clocktransmission system using the atomic oscillator according to theembodiment of the invention.

FIG. 13 is a perspective view showing the configuration of a movingobject (vehicle) including the atomic oscillator according to theembodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a quantum interference device, an atomic oscillator, and amoving object according to the invention will be described in detailbased on the embodiments with reference to the accompanying diagrams.

1. Atomic Oscillator (Quantum Interference Device)

First, an atomic oscillator according to the invention (atomicoscillator including a quantum interference device according to theinvention) will be described. In addition, an example where the quantuminterference device according to the invention is applied to an atomicoscillator will be described below. However, the quantum interferencedevice according to the invention is not limited thereto, and can beapplied to, for example, a magnetic sensor and a quantum memory as wellas the atomic oscillator.

First Embodiment

FIG. 1 is a cross-sectional view showing an atomic oscillator (quantuminterference device) according to a first embodiment of the invention,and FIG. 2 is a schematic diagram of the atomic oscillator shown inFIG. 1. In addition, FIG. 3 is a diagram for explaining the energy stateof alkali metal in a gas cell of the atomic oscillator shown in FIG. 1,and FIG. 4 is a graph showing the relationship between the frequencydifference of two light components from a light emitting portion and thedetection intensity in a light detecting portion for the light emittingportion and the light detecting portion of the atomic oscillator shownin FIG. 1. In addition, FIG. 5 is a cross-sectional view for explaininga heating portion and a connection member of the atomic oscillator shownin FIG. 1, FIG. 6 is an exploded view for explaining a gas cell and theconnection member of the atomic oscillator shown in FIG. 1, and FIG. 7is a plan view for explaining the gas cell and the connection member ofthe atomic oscillator shown in FIG. 1. In addition, FIG. 8A is a planview for explaining a support member of the atomic oscillator shown inFIG. 1, and FIG. 8B is a cross-sectional view taken along the line A-Ain FIG. 8A.

Hereinafter, for convenience of explanation, an upper side and a lowerside in FIG. 1 are referred to as “top” and “bottom”, respectively.

An atomic oscillator 1 shown in FIG. 1 is an atomic oscillator using aquantum interference effect.

As shown in FIG. 1, the atomic oscillator 1 includes a unit portion 2that forms a main portion to cause a quantum interference effect, apackage 3 in which the unit portion 2 is housed, and a support member 4that is housed in the package 3 and supports the unit portion 2 againstthe package 3.

Here, the unit portion 2 includes a gas cell 21, a light emittingportion 22, optical components 231 and 232, a light detecting portion24, a heater 25 (heating portion), a temperature sensor 26, a substrate28, and a connection member 29, and these are unitized.

Moreover, although not shown in FIG. 1, the atomic oscillator 1 includesa coil 27 and a control portion 5 in addition to those described above(refer to FIG. 2).

First, the principle of the atomic oscillator 1 will be describedbriefly.

In the atomic oscillator 1, alkali metal (metal atoms), such asrubidium, cesium, and sodium in a gaseous state, is sealed in the gascell 21.

As shown in FIG. 3, alkali metal has an energy level of the three levelsystem, and can take three states of two ground states (ground states 1and 2) of different energy levels and an excited state. Here, the groundstate 1 is an energy state lower than the ground state 2.

When two types of resonance light components 1 and 2 having differentfrequencies are emitted to such gaseous alkali metal, the lightabsorption rate (light transmittance) in alkali metal of the resonancelight components 1 and 2 changes depending on a difference (ω1−ω2)between the frequency ω1 of the resonance light 1 and the frequency ω2of the resonance light 2.

In addition, when the difference (ω1−ω2) between the frequency ω1 of theresonance light 1 and the frequency ω2 of the resonance light 2 matchesa frequency equivalent to the energy difference between the groundstates 1 and 2, each excitation from the ground states 1 and 2 to theexcited state is stopped. In this case, both the resonance lightcomponents 1 and 2 are transmitted through the alkali metal withoutbeing absorbed by the alkali metal. Such a phenomenon is called a CPTphenomenon or an electromagnetically induced transparency (EIT)phenomenon.

The light emitting portion 22 emits two types of light components(resonance light 1 and resonance light 2), which have differentfrequencies as described above, toward the gas cell 21.

For example, as the light emitting portion 22 changes the frequency ω2of the resonance light 2 in a state where the frequency ω1 of theresonance light 1 is fixed, when the difference (ω1−ω2) between thefrequency ω1 of the resonance light 1 and the frequency ω2 of theresonance light 2 matches a frequency WO equivalent to the energydifference between the ground states 1 and 2, the detection intensity ofthe light detecting portion 24 rises steeply as shown in FIG. 4. Such asteep signal is detected as an EIT signal. The EIT signal has a uniquevalue determined by the type of alkali metal. Accordingly, by using theEIT signal, it is possible to form an oscillator.

Hereinafter, each portion of the atomic oscillator 1 will be describedin detail in a sequential manner.

Gas Cell

In the gas cell 21, alkali metal (metal atoms), such as rubidium,cesium, and sodium in a gaseous state, is sealed.

As shown in FIG. 5, the gas cell 21 includes a body portion 211 having acolumnar through hole and a pair of window portions 212 and 213 thatblock both openings of the through hole. In this manner, internal spaceS where the alkali metal described above is sealed is formed.

Here, the body portion 211 forms a side wall that forms the internalspace S together with the two window portions 212 and 213. In addition,each of the window portions 212 and 213 of the gas cell 21 allowsexcitation light from the light emitting portion 22 to be transmittedtherethrough. In addition, excitation light incident on the gas cell 21is transmitted through one window portion 212, and excitation lightemitted from the gas cell 21 is transmitted through the other windowportion 213.

A constituent material of the window portions 212 and 213 is notparticularly limited as long as the material allows excitation light tobe transmitted therethrough as described above. For example, a glassmaterial, crystal, and the like can be mentioned.

In addition, a constituent material of the body portion 211 of the gascell 21 is not particularly limited. For example, a metal material, aresin material, and the like may be used, or a glass material andcrystal may be used similar to the window portions 212 and 213.

In addition, the window portions 212 and 213 are airtightly bonded tothe body portion 211. Therefore, the internal space S of the gas cell 21can be formed as airtight space.

A method of bonding the body portion 211 and the window portions 212 and213 of the gas cell 21 is determined depending on their constituentmaterials. Although the method is not limited in particular, forexample, a bonding method using an adhesive, a direct bonding method, ananodic bonding method, and the like can be used.

In addition, a heat transfer layer 214 is provided on the surface of thewindow portion 212 of the gas cell 21. Similarly, a heat transfer layer215 is provided on the surface of the window portion 213 of the gas cell21.

Each of the heat transfer layers 214 and 215 is formed of a materialhaving a larger thermal conductivity than the constituent material thatforms the window portions 212 and 213. Thus, since the heat transferlayers 214 and 215 contain a material, which has a larger thermalconductivity than a material that forms the window portions 212 and 213,on the surface of the window portions 212 and 213, heat from theconnection member 29 can be efficiently diffused by thermal conductiondue to the heat transfer layers 214 and 215. As a result, it is possibleto make the temperature distribution of each of the window portions 212and 213 uniform.

In the present embodiment, the heat transfer layers 214 and 215 areprovided on the outer surface side of the gas cell 21. Therefore, theconnection member 29 can be brought into contact with each of the heattransfer layers 214 and 215. Therefore, the transfer of heat from theconnection member 29 to each of the heat transfer layers 214 and 215 canbe efficiently performed. As a result, since it is possible to preventthe gaseous alkali metal from being condensed on the light passingsurface of the gas cell 21, it is possible to improve the stabilitycharacteristics of the atomic oscillator 1.

In addition, the same heat transfer layer as the heat transfer layers214 and 215 may also be provided on the inner surface of each of thewindow portions 212 and 213. In this case, it is possible to make thetemperature distribution of each of the window portions 212 and 213uniform more efficiently.

In addition, the heat transfer layers 214 and 215 allow excitation lightto be transmitted therethrough. Accordingly, excitation light from theoutside of the gas cell 21 can be made to be incident on the gas cell 21through the heat transfer layer 214 and the window portion 212. Inaddition, excitation light from the inside of the gas cell 21 can beemitted to the outside of the gas cell 21 through the window portion 213and the heat transfer layer 215.

A constituent material of the heat transfer layers 214 and 215 is notparticularly limited as long as the material has a larger thermalconductivity than the constituent material of the window portions 212and 213 and allows excitation light to be transmitted through the heattransfer layers 214 and 215. For example, diamond, diamond-like carbon(DLC), and the like can be used.

Light Emitting Portion

The light emitting portion 22 has a function of emitting excitationlight to excite alkali metal atoms in the gas cell 21.

More specifically, the light emitting portion 22 emits two types oflight components (resonance light 1 and resonance light 2) havingdifferent frequencies as described above.

The frequency ω1 of the resonance light 1 is for exciting the alkalimetal in the gas cell 21 from the ground state 1 to the excited statedescribed above.

In addition, the frequency ω2 of the resonance light 2 is for excitingthe alkali metal in the gas cell 21 from the ground state 2 to theexcited state described above.

As the light emitting portion 22, there is no particular limitation aslong as the excitation light can be emitted as described above. Forexample, a semiconductor laser, such as a vertical cavity surfaceemitting laser (VCSEL), can be used.

Optical Component

As shown in FIG. 2, each of the plurality of optical components 231 and232 is provided on the optical path of excitation light LL between thelight emitting portion 22 and the gas cell 21.

In the present embodiment, the optical components 231 and 232 aredisposed in this order from the light emitting portion 22 side to thegas cell 21 side.

The optical component 231 is a λ/4 wave plate. Accordingly, theexcitation light LL from the light emitting portion 22 can be convertedfrom linearly polarized light to circularly polarized light(right-handed circularly polarized light or left-handedcircularly-polarized light).

As will be described later, if excitation light of linearly polarizedlight is emitted to alkali metal atoms in a state where the alkali metalatoms in the gas cell 21 are Zeeman splitting due to the magnetic fieldof the coil 27, the alkali metal atoms are present so as to be evenlydispersed in a plurality of Zeeman-split levels by interaction betweenthe excitation light and the alkali metal atom. For this reason, sincethe number of alkali metal atoms in a desired energy level is reducedrelative to the number of alkali metal atoms in another energy level,the number of atoms to cause a desired EIT phenomenon is reduced, andthe strength of a desired EIT signal is reduced. As a result, theoscillation characteristics of the atomic oscillator 1 are degraded.

In contrast, as will be described later, if excitation light ofcircularly polarized light is emitted to alkali metal atoms in a statewhere the alkali metal atoms in the gas cell 21 are Zeeman splitting dueto the magnetic field of the coil 27, the number of alkali metal atomsin a desired energy level of a plurality of levels of the alkali metalatoms Zeeman splitting can be increased relative to the number of alkalimetal atoms in another energy level by interaction between theexcitation light and the alkali metal atom. For this reason, the numberof atoms to cause a desired EIT phenomenon is increased, and thestrength of a desired EIT signal is increased. As a result, theoscillation characteristics of the atomic oscillator 1 are improved.

The optical component 232 is a dimming filter (ND filter). Therefore,the intensity of the excitation light LL incident on the gas cell 21 canbe adjusted (reduced). For this reason, even if the output of the lightemitting portion 22 is large, the amount of excitation light incident onthe gas cell 21 can be set to the desired amount of light. In thepresent embodiment, the intensity of the excitation light LL havingpolarized light in a predetermined direction, which has passed throughthe optical component 231, is adjusted by the optical component 232.

In addition, between the light emitting portion 22 and the gas cell 21,not only the wave plate and the dimming filter but also other opticalcomponents, such as a lens and a polarizing plate, may be disposed. Inaddition, depending on the intensity of excitation light from the lightemitting portion 22, the optical component 232 may be omitted.

Light Detecting Portion

The light detecting portion 24 has a function of detecting the intensityof the excitation light LL (resonance light components 1 and 2)transmitted through the gas cell 21.

In the present embodiment, the light detecting portion 24 is bonded tothe connection member 29 with an adhesive 30 interposed therebetween.

Here, a known adhesive can be used as the adhesive 30. However, by usingan adhesive with excellent thermal conductivity, it is also possible toadjust the temperature of the light detecting portion 24 by the heatfrom the connection member 29. On the other hand, when using an adhesivewith excellent thermal insulation, it is possible to suppress heatinterference between the connection member 29 and the light detectingportion 24.

As the light detecting portion 24, there is no particular limitation aslong as the excitation light can be detected as described above. Forexample, an optical detector (light receiving element), such as a solarbattery and a photodiode, can be used.

Heater

The heater 25 is a heating resistor (heating portion) that generatesheat by current application.

Heat from the heater 25 is transferred to the gas cell 21 through thesubstrate 28 and the connection member 29. As a result, the gas cell 21(more specifically, alkali metal in the gas cell 21) is heated, and thealkali metal in the gas cell 21 can be maintained in a gas state. Inaddition, in the present embodiment, heat from the heater 25 is alsotransferred to the light emitting portion 22 through the substrate 28.

The heater 25 is separated from the gas cell 21. Accordingly, it ispossible to suppress a situation where the unnecessary magnetic fieldcaused by the application of current to the heater 25 has an adverseeffect on the metal atoms in the gas cell 21.

In the present embodiment, the heater 25 is provided on the substrate28. In this case, heat from the heater 25 is transferred to thesubstrate 28.

In addition, in the present embodiment, the heater 25 is separated froma part of the connection member 29 so as to face each other.Accordingly, heat from the heater 25 can be efficiently transferred tothe connection member 29, the gas cell 21, and the like. In addition,the heater 25 may face a part of the connection member 29, and may beconnected to a part of the connection member 29.

In addition, it is also possible to use a Peltier element instead of theheater 25 or together with the heater 25. In this case, a heating sideportion of the Peltier element forms a heating portion.

Temperature Sensor

The temperature sensor 26 detects the temperature of the heater 25 orthe gas cell 21. In addition, the amount of heat generation of theheater 25 is controlled on the basis of the detection result of thetemperature sensor 26. In this manner, it is possible to maintain alkalimetal atoms in the gas cell 21 at a desired temperature.

In the present embodiment, the temperature sensor 26 is provided on thesubstrate 28.

In addition, the installation position of the temperature sensor 26 isnot limited thereto. For example, the temperature sensor 26 may beprovided on the connection member 29, or may be provided on the heater25, or may be provided on the outer surface of the gas cell 21.

As the temperature sensor 26, various known temperature sensors, such asa thermistor and a thermocouple, can be used without being particularlylimited.

Coil

The coil 27 has a function of generating a magnetic field by currentapplication. Accordingly, by applying a magnetic field to the alkalimetal in the gas cell 21, a gap between the degenerate different energylevels of the alkali metal is spread by Zeeman splitting, thereby beingable to improve the resolution. As a result, it is possible to improvethe accuracy of the oscillation frequency of the atomic oscillator 1.

In addition, the magnetic field generated by the coil 27 may be either aDC magnetic field or an AC magnetic field, or may be a magnetic field inwhich the DC magnetic field and the AC magnetic field are superimposed.

In addition, the coil 27 may be a solenoid coil provided so as tosurround the gas cell 21, or may be a Helmholtz coil provided so as tointerpose the gas cell 21.

Although the installation position of the coil 27 is not shown in thediagram, the coil 27 may be provided between the gas cell 21 and theconnection member 29, or may be provided between the connection member29 and the package 3.

Substrate

The light emitting portion 22, the heater 25, the temperature sensor 26,and the connection member 29 are mounted on one surface (top surface) ofthe substrate 28.

The substrate 28 has a function of transferring the heat from the heater25 to the connection member 29. Accordingly, even if the heater 25 isseparated from the connection member 29, the heat from the heater 25 canbe transferred to the connection member 29.

Here, the substrate 28 thermally connects the heater 25 and theconnection member 29 to each other. Thus, by mounting the heater 25 andthe connection member 29 on the substrate 28, it is possible to increasethe degree of freedom of installation of the heater 25.

In addition, since the light emitting portion 22 is mounted on thesubstrate 28, it is possible to adjust the temperature of the lightemitting portion 22 by the heat from the heater 25.

In addition, the substrate 28 also has a function of supporting thelight emitting portion 22, the heater 25, the temperature sensor 26, andthe connection member 29.

A constituent material of the substrate 28 is not particularly limited,and a material with excellent thermal conductivity, for example, a metalmaterial can be used. In addition, when the substrate 28 is formed of ametal material, an insulating layer formed of, for example, a resinmaterial, a metal oxide, or a metal nitride may be provided on thesurface of the substrate 28 as necessary.

In addition, the substrate 28 can be omitted depending on the shape ofthe connection member 29, the installation position of the heater 25,and the like. In this case, the heater 25 may be provided at a positionwhere the heater 25 is brought into contact with the connection member29.

Connection Member

The connection member 29 thermally connects the heater 25 and each ofthe window portions 212 and 213 of the gas cell 21. Accordingly, sincethe heat from the heater 25 is transferred to the window portions 212and 213 by thermal conduction by the connection member 29, each of thewindow portions 212 and 213 can be heated. In addition, the heater 25and the gas cell 21 can be separated from each other. In this case, itis possible to suppress a situation where the unnecessary magnetic fieldcaused by the application of current to the heater 25 has an adverseeffect on the metal atoms in the gas cell 21. In addition, since thenumber of heaters 25 can be reduced, the number of wiring lines for theapplication of current to the heater 25 can be reduced. As a result, itis possible to miniaturize the atomic oscillator 1 (quantum interferencedevice).

As shown in FIG. 5, the connection member 29 is formed by a pair ofconnection members 291 and 292 provided with the gas cell 21 interposedtherebetween. Accordingly, heat can be uniformly transferred from theconnection member 29 to each of the window portions 212 and 213 of thegas cell 21 while simplifying the installation of the connection member29 with respect to the gas cell 21.

More specifically, the connection member 291 includes a pair ofconnection portions 291 a and 291 b, which are disposed with the gascell 21 interposed therebetween in a direction in which the two windowportions 212 and 213 are aligned, and a connecting portion 291 c thatconnects the pair of connection portions 291 a and 291 b to each other.Similarly, the connection member 292 includes a pair of connectionportions 292 a and 292 b, which are disposed with the gas cell 21interposed therebetween in a direction in which the two window portions212 and 213 are aligned, and a connecting portion 292 c that connectsthe pair of connection portions 292 a and 292 b to each other.Accordingly, heat from the heater 25 can be efficiently transferred toeach of the window portions 212 and 213.

Here, each of the connection portions 291 a and 292 a is in contact withthe heat transfer layer 214. Similarly, each of the connection portions291 b and 292 b is in contact with the heat transfer layer 214.

That is, the window portion 212 and each of the connection members 291and 292 are connected to each other through the heat transfer layer 214.Similarly, the window portion 213 and each of the connection members 291and 292 are connected to each other through the heat transfer layer 215.Accordingly, heat from the connection members 291 and 292 can beefficiently transferred to the window portions 212 and 213.

In addition, each of the connection portions 291 a, 291 b, 292 a, and292 b is formed so as to avoid the passage area of the excitation lightLL. That is, each of the connection portions 291 a, 291 b, 292 a, and292 b is disposed outside the passage area of the excitation light LL.Accordingly, it is possible to make excitation light incident on the gascell 21 while emitting the excitation light from the gas cell 21.

In the present embodiment, when viewed from a direction parallel to theaxis a of the excitation light LL, the connection portions 291 a, 291 b,292 a, and 292 b are located outside the internal space S. Therefore,the passage area of the excitation light LL can be increased.

Such a pair of connection members 291 and 292 are fitted so as tointerpose the gas cell 21 from both sides of a pair of side surfaces,which face each other, of the gas cell 21, for example, as shown in FIG.6.

The connection members 291 and 292 before being fitted are designed suchthat the distance between the connection portions 291 a and 291 b in theconnection member 291 and the distance between the connection portions292 a and 292 b in the connection member 292 are equal to or slightlysmaller than the distance between the outer surface of the heat transferlayer 214 and the outer surface of the heat transfer layer 215 in thegas cell 21 (distance between the outer surface of the window portion212 and the outer surface of the window portion 213 when the heattransfer layers 214 and 215 are omitted). In addition, the connectingportions 291 c and 292 c are elastically deformed as necessary, so thatthe connection members 291 and 292 are fitted to the gas cell 21 asdescribed above. In this manner, each of the connection portions 291 aand 292 a can be brought into contact with the heat transfer layer 214(the window portion 212 when the heat transfer layers 214 and 215 areomitted), and each of the connection portions 291 b and 292 b can bebrought into contact with the heat transfer layer 214 (the windowportion 212 when the heat transfer layers 214 and 215 are omitted).

In addition, when a gap is formed at least either between the heattransfer layer 214 and the connection portions 291 a and 292 a orbetween the heat transfer layer 215 and the connection portions 291 band 292 b, an adhesive with thermal conductivity may be filled in thegap. As examples of the adhesive, metal paste, a resin based adhesivecontaining a thermally conductive filler, and a silicone resin basedadhesive can be mentioned. By using such an adhesive, it is possible tohave excellent thermal conductivity between the heat transfer layer 214and the connection portions 291 a and 292 a or between the heat transferlayer 215 and the connection portions 291 b and 292 b even if a gap isformed between the heat transfer layer 214 and the connection portions291 a and 292 a or between the heat transfer layer 215 and theconnection portions 291 b and 292 b. In addition, even if such a gap isnot formed, the connection members 291 and 292 can be fixed to the gascell 21 using the above-described adhesive. In addition, such anadhesive can also be filled between the connection members 291 and 292.

In addition, each of the connecting portions 291 c and 292 c is disposedsuch that a gap is formed between each of the connecting portions 291 cand 292 c and the gas cell 21. That is, each of the connection portions291 c and 292 c has a portion separated from the gas cell 21. In thiscase, since the transfer of heat between each of the connecting portions291 c and 292 c and the gas cell 21 can be suppressed, heat can beefficiently transferred from the connection members 291 and 292 to thewindow portions 212 and 213.

As a constituent material of the connection member 29, a material havinga larger thermal conductivity than a material that forms the bodyportion 211 of the gas cell 21 may be used. For example, a metalmaterial, which is a material with excellent thermal conductivity, canbe used. In addition, for example, it is possible to use soft magneticmaterials, such as Fe and various Fe alloys (silicon iron, permalloy,amorphous, Sendust). Accordingly, it is possible to suppress a situationwhere the unnecessary magnetic field caused by the application ofcurrent to the heater 25 has an adverse effect on the metal atoms in thegas cell 21. In addition, it is also possible to suppress themagnetization of an unnecessary magnetic field.

Package

The package 3 has a function of housing the unit portion 2 and thesupport member 4 therein. In addition, although not shown in FIG. 1, thecoil 27 shown in FIG. 2 is also housed in the package 3. In addition,components other than the components described above may be housed inthe package 3.

As shown in FIG. 1, the package 3 includes a plate-like base 31 (baseportion) and a bottomed cylindrical lid 32, and the opening of the lid32 is blocked by the base 31. Thus, a space where the unit portion 2 andthe support member 4 are housed is formed.

The base 31 supports the unit portion 2 through the support member 4.

In addition, although not shown, a plurality of wiring lines and aplurality of terminals for the application of current from the outsideof the package 3 to the internal unit portion 2 are provided in the base31.

A constituent material of the base 31 is not particularly limited. Forexample, a resin material, a ceramic material, and the like can be used.

The lid 32 is bonded to the base 31.

A method of bonding the base 31 and the lid 32 to each other is notparticularly limited. For example, brazing, seam welding, energy beamwelding (laser welding, electron beam welding, and the like), and thelike can be used.

In addition, a bonding member for bonding the base 31 and the lid 32 toeach other may be interposed between the base 31 and the lid 32.

A constituent material of the lid 32 is not particularly limited. Forexample, a resin material, a ceramic material, a metal material, and thelike can be used.

In addition, it is preferable that the base 31 and the lid 32 areairtightly bonded to each other. That is, it is preferable that theinside of the package 3 is airtight space. In this case, the inside ofthe package 3 can be changed to a decompressed state or an inert gasfilled state. As a result, the characteristics of the atomic oscillator1 can be improved.

In particular, it is preferable that the inside of the package 3 is in adecompressed state.

In this case, it is possible to suppress the transfer of heat throughthe space in the package 3. Therefore, it is possible to suppress thethermal interference between the heater 25 and the gas cell 21 throughthe space in the package 3 or between the connection member 29 and theoutside of the package 3. As a result, since the heat from the heater 25is efficiently transferred to the window portions 212 and 213 throughthe connection member 29, it is possible to reduce the temperaturedifference between the two window portions 212 and 213.

In addition, the transfer of heat between the unit portion 2 and theoutside of the package 3 can be suppressed more effectively.

Support Member 4

The support member 4 is housed in the package 3, and has a function ofsupporting the unit portion 2 against the base 31 that forms a part ofthe package 3.

In addition, the support member 4 has a function of suppressing thetransfer of heat between the unit portion 2 and the outside of thepackage 3.

As shown in FIGS. 8A and 8B, the support member 4 includes a pluralityof leg portions 41 (column portions) and a connecting portion 42 thatconnects the plurality of leg portions 41 to each other.

Each of the plurality of leg portions 41 is bonded to the inner surfaceof the base 31 in the package 3 by an adhesive, for example.

The plurality of leg portions 41 are disposed outside the unit portion 2in plan view from a direction in which the base 31 and the unit portion2 overlap each other (hereinafter, also simply referred to as “in planview”).

In the present embodiment, four leg portions 41 are provided so as tocorrespond to the corners of the gas cell 21 that forms a square in planview.

Each leg portion 41 has a cylindrical shape, and is erected so as toextend in a direction perpendicular to the inner surface of the base 31.

In addition, a hollow portion 411 is formed in each leg portion 41.Therefore, it is possible to suppress the transfer of heat in each legportion 41 while ensuring the rigidity of each leg portion 41.

It is preferable that the hollow portion 411 is in an atmospheredecompressed from the atmospheric pressure (decompressed state or vacuumstate). In this case, it is possible to suppress the transfer of heat ineach leg portion 41 more effectively.

In the present embodiment, the hollow portion 411 extends up and downthrough the leg portion 41. Therefore, by changing the inside of thepackage 3 to a decompressed state, the inside of the hollow portion 411can also be changed to the decompressed state.

In addition, when the upper side of the hollow portion 411 is not open,if a gap for making the inside and outside of the hollow portion 411communicate with each other is formed between each leg portion 41 andthe base 31, the inside of the hollow portion 411 can also be changed tothe decompressed state by changing the inside of the package 3 to thedecompressed state.

The connection portion 42 connects the upper ends (one ends) of theplurality of leg portions 41. As a result, it is possible to increasethe rigidity of the support member 4. In the present embodiment, theconnecting portion 42 is formed integrally with the plurality of legportions 41. In addition, the connecting portion 42 may be formedseparately from the plurality of leg portions 41 and be bonded to eachleg portion 41 by an adhesive, for example.

The entire connecting portion 42 has a plate shape. In this manner, itis possible to increase the rigidity of the support member 4 with arelatively simple structure.

In addition, the connecting portion 42 has a rectangular shape so thatthe four leg portions 41 are located in the corners in plan view.

The unit portion 2 (more specifically, the substrate 28) is bonded(connected) to the top surface (surface on the opposite side to the legportion 41) of the connecting portion 42. As a result, the unit portion2 is supported by the support member 4.

A connection portion between the connecting portion 42 and the unitportion 2 is located on the inner side than the upper ends (one ends) ofthe plurality of leg portions 41 in plan view.

A recess 421 is formed in a central portion of the top surface (that is,a surface on the side of the unit portion 2) of the connecting portion42.

Space in the recess 421 is located between the unit portion 2 and theconnecting portion 42. In this case, since the contact area of the unitportion 2 and the connecting portion 42 is reduced, it is possible tosuppress the transfer of heat between the connecting portion 42 and theunit portion 2 effectively. In addition, it is also possible to suppressthe transfer of heat in the connecting portion 42.

In the present embodiment, the recess 421 is disposed on the inner sidethan the outer portion of the unit portion 2 in plan view. Accordingly,the unit portion 2 is bonded to a portion of the connecting portion 42on the outer peripheral side than the recess 421. In addition, therecess 421 may have a portion located outside the outer portion of theunit portion 2 in plan view.

In addition, it is preferable that the inside of the recess 421 is in adecompressed state. In this case, since the thermal insulation in therecess 421 is improved, it is possible to suppress the escape of heatfrom the unit portion 2 to the connecting portion 42.

Although the connection portion between the unit portion 2 and thesupport member 4 may be formed on the entire circumference along theouter periphery of the recess 421, it is preferable to form a pluralityof connection portions in a spot shape from the point of view thatthermal conduction between the unit portion 2 and the support member 4through the connection portion is suppressed.

In addition, it is preferable that a gap for making the inside andoutside of the recess 421 communicate with each other be formed betweenthe unit portion 2 and the support member 4. Therefore, by changing theinside of the package 3 to a decompressed state, the inside of therecess 421 can also be changed to the decompressed state.

According to the support member 4, the lower end (other end) of each legportion 41 is separated from the unit portion 2 in plan view. Therefore,the support member 4 has a portion in which the heat transfer path(hereinafter, referred to as a “heat transfer path of the support member4”) from a connection portion between the unit portion 2 and the supportmember 4 to the lower end of each leg portion 41 is bent or curved.

In this case, even if the distance between the base 31 and the unitportion 2 is reduced, it is possible to increase the heat transfer pathfrom the unit portion 2 to the base 31 through the support member 4. Asa result, it is possible to suppress the transfer of heat from the unitportion 2 to the base 31 through the support member 4 whileminiaturizing the atomic oscillator 1. In addition, since a plurality ofleg portions 41 are connected to each other by the connecting portion42, it is possible to increase the rigidity of the support member 4.Therefore, it is possible to suppress the vibration of the unit portion2.

In addition, assuming that the length of the heat transfer path of thesupport member 4 is L [m], the sum of the average cross-sectional areaof the support member 4 in the heat transfer path is A [m²], and thethermal conductivity of a material that forms the support member 4 is λ[W/(m·K)], it is preferable that the relationship of (thermalresistance)=(1/k)×(L/A)≧16800 [° C./W] is satisfied.

In this case, it is possible to suppress the transfer of heat from theunit portion 2 to the base 31 through the support member 4. In addition,since the power consumption of the heater 25 is reduced to 15 mW orless, it is possible to reduce the power consumption of the atomicoscillator 1. In addition, since the heater 25 can be made small, it ispossible to miniaturize the atomic oscillator 1. Therefore, the atomicoscillator 1 can be mounted in various apparatuses.

In addition, a constituent material of the support member 4 is notparticularly limited as long as the material has relatively low thermalconductivity and makes it possible for the support member 4 to haverigidity for supporting the unit portion 2. For example, it ispreferable to use non-metal materials, such as a resin material and aceramic material. More preferably, a resin material is used. When thesupport member 4 is formed of a resin material, even if the shape of thesupport member 4 is complicated, the support member 4 can be easilymanufactured using a known method, such as an injection molding method.In addition, the constituent material of the leg portion 41 and theconstituent material of the connecting portion 42 may be the same or maybe different.

A resin material that forms the support member 4 is not particularlylimited. For example, polyethylene, polyolefin such as ethylene-vinylacetate copolymer (EVA), an acryl-based resin,acrylonitrile-butadiene-styrene copolymer (ABS resin),acrylonitrile-styrene copolymer (AS resin), polyethylene terephthalate(PET), polyether, polyether ketone (PEK), polyether ether ketone (PEEK),various kinds of thermoplastic elastomers including a styrene-basedelastomer, a polyolefin-based elastomer, a polyvinyl chloride-basedelastomer, a polyurethane-based elastomer, a polyester-based elastomer,a polyamide-based elastomer, a polybutadiene-based elastomer, atrans-polyisoprene-based elastomer, a fluororubber-based elastomer, anda chlorinated polyethylene-based elastomer, an epoxy resin, a phenolresin, an urea resin, a melamine resin, unsaturated polyester, asilicone resin, polyurethane, and copolymers, blends, and polymeralloys, which are mainly composed of the above materials, can bementioned. In addition, one or two or more of these can be used incombination (for example, as a laminate of two or more layers).

In addition, it is preferable that the thermal conductivity of thesupport member 4 is equal to or greater than 0.1 W·m⁻¹·K⁻¹ and equal toor less than 40 W·m⁻¹·K⁻¹. More preferably, the thermal conductivity ofthe support member 4 is equal to or greater than 0.1 W·m⁻¹·K⁻¹ and equalto or less than 0.5 W·m⁻¹·K⁻¹. Thus, thermal conduction between the unitportion 2 and the package 3 through the support member 4 can besuppressed more effectively. That is, it is possible to make the effectof thermally separating the unit portion 2 from the package 3 noticeableby improving the thermal insulation of the support member 4.

In addition, it is preferable that processing for increasing thereflectance of heat is performed on the surface of at least one of theleg portion 41 and the connecting portion 42. In this case, it ispossible to suppress the transfer of heat due to radiation between thesupport member 4 and other members (in particular, the base 31).

Such processing for increasing the reflectance of heat is notparticularly limited. For example, processing for forming a metal filmon the surface of the support member 4 can be mentioned.

Control Portion

The control portion 5 shown in FIG. 2 has a function of controlling theheater 25, the coil 27, and the light emitting portion 22.

Such a control portion 5 includes an excitation light control portion 51that controls the frequencies of the resonance light components 1 and 2of the light emitting portion 22, a temperature control portion 52 thatcontrols the temperature of the alkali metal in the gas cell 21, and amagnetic field control portion 53 that controls a magnetic field appliedto the gas cell 21.

The excitation light control portion 51 controls the frequencies of theresonance light components 1 and 2 emitted from the light emittingportion 22 on the basis of a detection result of the light detectingportion 24 described above. More specifically, the excitation lightcontrol portion 51 controls the frequencies of the resonance lightcomponents 1 and 2 emitted from the light emitting portion 22 such that(ω1−ω2) detected by the light detecting portion 24 becomes theabove-described frequency WO unique to the alkali metal. In addition,the excitation light control portion 51 controls the center frequency ofthe resonance light components 1 and 2 emitted from the light emittingportion 22. Thus, it is possible to detect the EIT signal describedabove. In addition, the control portion 5 causes a signal of a crystaloscillator (not shown) to be output in synchronization with the EITsignal.

In addition, the temperature control portion 52 controls the applicationof current to the heater 25 on the basis of the detection result of thetemperature sensor 26. Thus, the gas cell 21 can be maintained in adesired temperature range.

In addition, the magnetic field control portion 53 controls theapplication of current to the coil 27 such that the magnetic fieldgenerated by the coil 27 is constant.

The control portion 5 is provided, for example, in an IC chip mounted ona substrate on which the package 3 is mounted. In addition, the controlportion 5 may also be provided in the package 3.

According to the atomic oscillator 1 of the present embodiment describedabove, since the heater 25 is thermally connected to each of the twowindow portions 212 and 213 of the gas cell 21 through the connectionmember 29, heat from the heater 25 can be transmitted to each of thewindow portions 212 and 213 by thermal conduction using the connectionmember 29 and each of the window portions 212 and 213 can be heated. Inaddition, the heater 25 and the gas cell 21 can be separated from eachother. In this case, it is possible to suppress a situation where theunnecessary magnetic field caused by the application of current to theheater 25 has an adverse effect on the metal atoms in the gas cell 21.In addition, since the number of heaters 25 can be reduced, the numberof wiring lines for the application of current to the heater 25 can bereduced. As a result, it is possible to miniaturize the atomicoscillator 1.

Second Embodiment

Next, a second embodiment of the invention will be described.

FIG. 9 is a cross-sectional view showing an atomic oscillator (quantuminterference device) according to the second embodiment of theinvention, and FIG. 10 is a plan view for explaining a gas cell and aconnection member of the atomic oscillator shown in FIG. 9.

The atomic oscillator according to the present embodiment is the same asthe atomic oscillator according to the first embodiment described aboveexcept that the configuration of the connection member and thearrangement of the light emitting portion are different.

Hereinafter, the atomic oscillator of the second embodiment will bedescribed focusing on the differences from the first embodiment, andexplanations on the same matters will be omitted. In addition, in FIGS.9 and 10, the same reference numerals are given to the same componentsas in the embodiment described above.

An atomic oscillator 1A shown in FIG. 9 includes a unit portion 2A thatforms a main portion to cause a quantum interference effect, a package 3in which the unit portion 2A is housed, and a support member 4 that ishoused in the package 3 and supports the unit portion 2A against thepackage 3.

Here, the unit portion 2A includes a gas cell 21, a light emittingportion 22, optical components 231 and 232, a light detecting portion24, a heater 25 (heating portion), a temperature sensor 26, a substrate28, and a connection member 29A, and these are unitized.

As shown in FIG. 10, the connection member 29A is configured to includea pair of connection members 291A and 292A provided with the gas cell 21interposed therebetween.

The pair of connection members 291A and 292A is configured so as tosurround the entire circumference of one window portion 213 of the gascell 21. In addition, although not shown, the pair of connection members291A and 292A is configured so as to surround the entire circumferenceof the other window portion of the gas cell 21. Therefore, it ispossible to make the temperature distribution of each window of the gascell 21 uniform more effectively.

In addition, although not shown, the pair of connection members 291A and292A is configured so as to surround the entire circumference of a bodyportion (not shown) of the gas cell 21.

In the present embodiment, a region surrounded by the pair of connectionmember 291A and 292A in plan view has a rectangular shape (morespecifically, a square shape) corresponding to the shape of the gas cell21. In addition, the shape of the region is not limited to therectangular shape, and may be a circular shape, for example.

As shown in FIG. 9, the heater 25 (heating portion) is provided on thesubstrate 28 on the opposite side to the gas cell 21. In this case, whenviewed from the emission direction of excitation light of the lightemitting portion 22, that is, in plan view, the heater 25 can bedisposed at a position overlapping the region of the gas cell 21 throughwhich excitation light passes. Therefore, the heat transfer path fromthe heater 25 to the region of the gas cell 21 through which excitationlight passes can be made to be equal in each portion in thecircumferential direction of each window portion of the gas cell 21.

In addition, in the present embodiment, it is preferable that thesubstrate 28 has a magnetic shielding property. Accordingly, it ispossible to suppress a situation where the unnecessary magnetic fieldcaused by the application of current to the heater 25 has an adverseeffect on the metal atoms in the gas cell 21. In this case, as examplesof the constituent material of the substrate 28, soft magneticmaterials, such as Fe and various Fe alloys (silicon iron, permalloy,amorphous, Sendust), may be used.

Here, the substrate 28 may be formed integrally with the connectionmember 29A, or may form a part of the connection member 29A.Accordingly, the connection member 29A contains a soft magneticmaterial, and at least a part (substrate 28) is disposed between the gascell 21 and the heater 25. As a result, it is possible to prevent amagnetic field from the heater 25 from reaching the gas cell 21.

According to the atomic oscillator 1A of the second embodiment describedabove, it is also possible to realize miniaturization while suppressingthe influence of an unnecessary magnetic field from the heater 25, whichgenerates heat by current application, on the gas cell 21.

2. Electronic Apparatus

The atomic oscillator according to the invention described above can beassembled into various kinds of electronic apparatuses. Such anelectronic apparatus including the atomic oscillator according to theinvention has excellent reliability.

Hereinafter, an example of the electronic apparatus including the atomicoscillator according to the invention will be described.

FIG. 11 is a diagram showing the schematic configuration when the atomicoscillator according to the invention is used in a positioning systemusing a GPS Satellite.

A positioning system 100 shown in FIG. 11 is configured to include a GPSsatellite 200, a base station apparatus 300, and a GPS receiver 400.

The GPS satellite 200 transmits positioning information (GPS signal).

The base station apparatus 300 includes a receiving apparatus 302 thatreceives positioning information from the GPS satellite 200 with highaccuracy through an antenna 301 disposed in the electronic referencepoint (GPS continuous observation station), for example, and atransmission apparatus 304 that transmits the positioning informationreceived by the receiving apparatus 302 through an antenna 303.

Here, the receiving apparatus 302 is an electronic apparatus includingthe above-described atomic oscillator 1 according to the invention as areference frequency oscillation source. Such a receiving apparatus 302has excellent reliability. In addition, the positioning informationreceived by the receiving apparatus 302 is transmitted by thetransmission apparatus 304 in real time.

The GPS receiver 400 includes a satellite receiving unit 402 thatreceives the positioning information from the GPS satellite 200 throughan antenna 401 and a base station receiving unit 404 that receives thepositioning information from the base station apparatus 300 through anantenna 403.

FIG. 12 is a schematic diagram showing an example of a clocktransmission system using the atomic oscillator according to theinvention.

A clock transmission system 500 shown in FIG. 12 is for matching theclock of apparatuses in a network of time-division multiplexing, and isa system having a redundant configuration of the N (Normal) type and theE (Emergency) type.

The clock transmission system 500 includes a clock supply module (CSM)501 and a synchronous digital hierarchy (SDH) apparatus 502 of the Astation (high order (N type)), a clock supply module 503 and an SDHapparatus 504 of the B station (high order (E type)), and a clock supplymodule 505 and SDH apparatuses 506 and 507 of the C station (low order).

The clock supply module 501 includes the atomic oscillator 1, andgenerates an N type clock signal. The atomic oscillator 1 in the clocksupply module 501 generates a clock signal in synchronization withhighly precise clock signals from the master clocks 508 and 509including an atomic oscillator that uses cesium.

The SDH apparatus 502 transmits and receives a main signal on the basisof the clock signal from the clock supply module 501, and superimposesthe N type clock signal on the main signal and transmits the resultingsignal to the low-order clock supply module 505.

The clock supply module 503 includes the atomic oscillator 1, andgenerates an E type clock signal. The atomic oscillator 1 in the clocksupply module 503 generates a clock signal in synchronization withhighly precise clock signals from the master clocks 508 and 509including an atomic oscillator that uses cesium.

The SDH apparatus 504 transmits and receives a main signal on the basisof the clock signal from the clock supply module 503, and superimposesthe E type clock signal on the main signal and transmits the resultingsignal to the low-order clock supply module 505.

The clock supply module 505 receives the clock signals from the clocksupply modules 501 and 503, and generates a clock signal insynchronization with the received clock signals.

Here, the clock supply module 505 usually generates a clock signal insynchronization with the N type clock signal from the clock supplymodule 501. In addition, when there is a problem in the N type, theclock supply module 505 generates a clock signal in synchronization withthe E type clock signal from the clock supply module 503. By switchingthe clock signal from N type to E type as described above, it ispossible to ensure the stable clock supply. As a result, it is possibleto increase the reliability of the clock path network.

The SDH apparatus 506 transmits and receives a main signal on the basisof the clock signal from the clock supply module 505. Similarly, the SDHapparatus 507 transmits and receives a main signal on the basis of theclock signal from the clock supply module 505. In this manner, theapparatus of the C station can be made to synchronize with the apparatusof the A station or the B station.

3. Moving Object

In addition, the atomic oscillator according to the invention describedabove can be assembled into various kinds of moving objects. Such amoving object including the atomic oscillator according to the inventionhas excellent reliability.

Hereinafter, an example of the moving object of the invention will bedescribed.

FIG. 13 is a perspective view showing the configuration of a movingobject (vehicle) including the atomic oscillator according to theinvention.

A moving object 1500 shown in FIG. 13 includes a vehicle body 1501 andfour wheels 1502, and is configured to rotate the wheels 1502 using apower source (engine; not shown) provided in the vehicle body 1501. Theatomic oscillator 1 is built in the moving object 1500. In addition, onthe basis of an oscillation signal from the atomic oscillator 1, forexample, a control unit (not shown) controls the driving of the powersource.

In addition, electronic apparatuses or moving objects including theatomic oscillator according to the invention are not limited to thosedescribed above. For example, the atomic oscillator according to theinvention can also be applied to a mobile phone, a digital still camera,an ink jet type discharge apparatus (for example, an ink jet printer), apersonal computer (a mobile personal computer and a laptop personalcomputer), a television, a video camera, a video tape recorder, a carnavigation apparatus, a pager, an electronic diary (electronic diarywith a communication function is also included), an electronicdictionary, an electronic calculator, an electronic game machine, a wordprocessor, a workstation, a video phone, a television monitor forsecurity, electronic binoculars, a POS terminal, medical equipment (forexample, an electronic thermometer, a sphygmomanometer, a blood sugarmeter, an electrocardiographic measurement device, an ultrasonicdiagnostic apparatus, and an electronic endoscope), a fish detector,various measurement apparatuses, instruments (for example, instrumentsfor vehicles, aircraft, and ships), and a flight simulator.

While the quantum interference device, the atomic oscillator, and themoving object according to the invention have been described withreference to the illustrated embodiments, the invention is not limitedto these. For example, the configuration of each portion of theembodiments described above may be replaced with an arbitraryconfiguration having the same function, and an arbitrary configurationmay be added.

In addition, in the invention, arbitrary configurations of theembodiments described above may be combined.

What is claimed is:
 1. A quantum interference device, comprising: a gascell including two window portions having a light transmissive propertyand the gas cell sealing metal atoms therein; a light emitting portionthat emits light that is transmitted through the two window portions; aheating portion that generates heat; and a connection member thattransmits the heart from the heating portion to the two window portionswithout applying a current to the connection member.
 2. The quantuminterference device according to claim 1, wherein the two windowportions are opposite to each other.
 3. The quantum interference deviceaccording to claim 2, wherein the two window portions and the heatingportion are partially overlapped with each other in a plan view.
 4. Thequantum interference device according to claim 1, wherein the heatingportion transmits the heat to the light emitting portion.
 5. The quantuminterference device according to claim 1, wherein the two windowportions and the heating portion are partially overlapped with eachother in a plan view.
 6. The quantum interference device according toclaim 1, wherein the connection member contains a metal.
 7. The quantuminterference device according to claim 1, wherein the connection memberis configured with a plurality of connection members, the plurality ofconnection members and the heating portion are thermally connected toeach other via a thermal connection member.
 8. An atomic oscillator,comprising: the quantum interference device according to claim
 1. 9. Anatomic oscillator, comprising: the quantum interference device accordingto claim
 2. 10. A moving object, comprising: the quantum interferencedevice according to claim
 1. 11. A moving object, comprising: thequantum interference device according to claim 2.